คำตอบ - Long subtraction
คำอธิบายทีละขั้นตอน
1. Rewrite the numbers from top to bottom, aligned by their place values
| Place value | hundreds | tens | ones | . | tenths |
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| . |
2. Subtract the numbers using long subtraction method
Because the upper digit (6) in the tenths column is too small to get a positive difference, borrow 1 from the digit (4) in the next number place which becomes (3) and get (16).
| Place value | hundreds | tens | ones | . | tenths |
| 3 | 16 | ||||
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| . |
Subtract the numbers in the tenths column from the top number:
16-7=9
| Place value | hundreds | tens | ones | . | tenths |
| 3 | 16 | ||||
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| . | 9 |
Because the upper digit (3) in the ones column is too small to get a positive difference, borrow 1 from the digit (2) in the next number place which becomes (1) and get (13).
| Place value | hundreds | tens | ones | . | tenths |
| 1 | 13 | ||||
| 3 | 16 | ||||
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| . | 9 |
Subtract the numbers in the ones column from the top number:
13-5=8
| Place value | hundreds | tens | ones | . | tenths |
| 1 | 13 | ||||
| 3 | 16 | ||||
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| 8 | . | 9 |
Because the upper digit (1) in the tens column is too small to get a positive difference, borrow 1 from the digit (7) in the next number place which becomes (6) and get (11).
| Place value | hundreds | tens | ones | . | tenths |
| 6 | 11 | ||||
| 1 | 13 | ||||
| 3 | 16 | ||||
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| 8 | . | 9 |
Subtract the numbers in the tens column from the top number:
11-8=3
| Place value | hundreds | tens | ones | . | tenths |
| 6 | 11 | ||||
| 1 | 13 | ||||
| 3 | 16 | ||||
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| 3 | 8 | . | 9 |
Subtract the numbers in the hundreds column from the top number:
6-5=1
| Place value | hundreds | tens | ones | . | tenths |
| 6 | 11 | ||||
| 1 | 13 | ||||
| 3 | 16 | ||||
| 7 | 2 | 4 | . | 6 | |
| - | 5 | 8 | 5 | . | 7 |
| 1 | 3 | 8 | . | 9 |
The solution is: 138.9
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